On Jul. 31, 2014, a dump truck, driving with its box up, slammed into the overhead truss of the Burlington Skyway, a bridge forming part of the Queen Elizabeth Way, a major Canadian thoroughfare. The damage required closure of the highway and extensive repairs.
Such dump trucks are merely one example of a service vehicle which has an extendable service component (in this case the dump box). As used herein, the term “service vehicle” refers to a vehicle which can perform at least one specific service task beyond mere locomotion and transportation, and which is designed to travel between sites over conventional roadways.
The term “extendable service component” refers to a component of a service vehicle that is movable between a “home” configuration in which the component is stowed or otherwise positioned for safe travel by the service vehicle on a roadway, and one or more extended configurations for performing the service task(s). A dump truck is therefore a service vehicle, since it can not only transport material in its dump box but can also unilaterally unload such material at a work site (a service task) by tilting its dump box and opening the gate. The dump box is hence the extendable service component, which when fully down is in its home configuration and when raised is in an extended configuration. A ladder truck used in firefighting is another example of a service vehicle, with its ladder being its extendible service component. Other examples include mobile cranes (the crane arm being the extendable service component), street cleaning machines (for which the discharge gate is the extendible service component), and utilities boom trucks, often called “cherry pickers” (for which the boom arm is the extendible service component).
The operator of the service vehicle provides the first line of defense, and it is known to provide an alarm to alert the operator of a service vehicle if the operator inadvertently attempts to drive the service vehicle on a roadway with the extendable service component out of the home configuration. One problem with providing an alarm is that it is often the operator's own inattentiveness which led to driving in a non-homed condition, and that same inattentiveness may lead to the alarm being ignored as well. Another known approach is to provide an interlock to prevent a service vehicle from being driven at all when the extendable service component is out of the home configuration. Using an interlock may obviate the inattentiveness problem, but is inappropriate in cases where it may be necessary to drive, albeit at low speed, with the extendable service component extended. For example, a dump truck may drive forward slowly with its box raised so as to spread material over a target area. Thus, neither an alarm nor an interlock provide a satisfactory solution.